Allow to set a description for navigation items

We will introduce a navigation dashboard for root menu items which do not a have a URL but children.

library/Icinga/Web/Navigation/NavigationItem.php

@@ -88,6 +88,13 @@ class NavigationItem implements IteratorAggregate
      */
     protected $label;
 
+    /**
+     * The item's description
+     *
+     * @var string
+     */
+    protected $description;
+
     /**
      * This item's parent
      *
@@ -481,6 +488,30 @@ class NavigationItem implements IteratorAggregate
         return $this;
     }
 
+    /**
+     * Get the item's description
+     *
+     * @return  string
+     */
+    public function getDescription()
+    {
+        return $this->description;
+    }
+
+    /**
+     * Set the item's description
+     *
+     * @param   string  $description
+     *
+     * @return  $this
+     */
+    public function setDescription($description)
+    {
+        $this->description = $description;
+
+        return $this;
+    }
+
     /**
      * Set this item's url target
      *